1. Field of the Invention
The present invention relates to a lens barrel.
2. Description of Related Art
As a conventional art, it is known a lens barrel having a structure of moving lenses so as to perform focusing, zooming, and the like. In JP2012-145827A, for example, it is disclosed a structure of moving lenses, in which a lens holding frame for holding a lens to be moved is accommodated in cam barrels having cam grooves formed therein and in straight barrels having straight guide grooves formed therein, and the lens holding frame includes cam followers that are engaged with the cam grooves and the straight guide grooves. When the cam barrels are rotated, the lenses are moved in a direction of an optical axis.
However, in the case of the structure in which the cam grooves and the cam followers are engaged with each other, the cam followers need to be smoothly slid with respect to the cam grooves. Thus, the cam followers need to have diameters somewhat smaller than groove widths of the cam grooves. In other words, gaps need to be secured between circumferential surfaces of the cam followers and cam surfaces of the cam grooves. Therefore, differences (gaps) between those surfaces may cause backlash of the cam followers with respect to the cam grooves, tilting of the lens holding frame, variation in degree of the tilting of the lens holding frame, and the like. As a result, performance of the lenses may become unstable. In particular, in a case of a zoom lens, when the backlash, the tilting, and the variation in degree of the tilting occur in a fast lens, performance of the lens is significantly influenced.